WOODLAND, Wash. -- Pasture renovation was on the minds of a couple of dozen people gathered at Robert Zumstein's farm, and Zumstein was proud to show off his hay fields.

As the visitors gathered at one of his fields, he said the 1/3-acre slope used to be covered by Canada thistle, a pernicious weed that spreads through a sprawling root system. Now the field was covered by a mix of tall fescue, perennial ryegrass, annual ryegrass and clover, ready to cut and virtually weed-free.

Gene Pirelli, with Oregon State University Extension, stood in the chest-tall grass during the June 26 pasture walk and described the renovation.

After the weedy field was sprayed for several years to kill off the thistle, Zumstein tilled it for two more years. "When you clean up a pasture, it may have 20 years of weed seed in it," Pirelli said. "Tillage is one means of control."

The cleaned plot was planted to potatoes, yielding 5,000 pounds.

Then last fall the hay farmer planted a pasture seed mix, whose first fruits are now ready to be harvested.

"You manage the pasture based on the variety of the mix," Pirelli said. "The more varieties, the more difficult to manage. I prefer simpler mixes. If you have enough pasture, you can buy just what you need and mix your own. I prefer a grass and a clover, or two grasses and a clover."

He described a few attributes of some of the varieties:

* Perennial ryegrass and timothy are highly palatable; orchardgrass is in the middle; and tall fescue is least palatable, though newer varieties are readily eaten.

* Annual ryegrass is popular in fall seed mixtures because it comes up quickly and shelters the slower-starting perennials. "Though it's called an annual, it's more of a short-term perennial. It can last up to three years," he said.

* White clover is a long-lasting perennial. Red clover is a good forage producer and becomes established sooner, but it doesn't last as long as white.

* Velvet grass is undesirable, though some cattle will eat it when it's very young. "Westside cattle would rather starve to death," he said.

* Timothy is better as a hay crop than as a pasture grass. It complicates a mix because it loves water and because it cannot tolerate close grazing.

Grazing, Pirelli said, is a critical part of managing a pasture, pulling the animals off before they damage the crop.

"Three inches belong to the plant. You graze above that," he stressed. Go too far and the plant won't survive the winter.

A second reason to take the animals off the grass in winter is they just physically can't get enough to eat off short grass.

Though most of the people on the pasture walk said they raise animals, he said, "You are more grass farmers than stockmen. The animal is a harvesting tool."

Pirelli pointed out the first-year crop in the former thistle patch.

"The first year, you treat it like a baby," he said. "You might graze it lightly, but you need to get the seed established, then take care of the young plants.

"The worst weed infestations occur on overgrazed pasture."

Ron Hendrickson, lead field inspector with the Clark County vegetation department, described some of the weeds to be aware of and how to deal with them.

"After grazing, you'll see the cows have left what they don't want to eat: thistles and other weeds," he said. "So you'll have to use mechanical control after rotating the animals off."

"You've got both false and regular dandelions. Regular dandelions have upright foliage, and you can see a milky substance when you break a stem. You can live with it in your pasture. The false dandelion has a tall shoot and flat leaves. It covers a big spot of ground, so you can't grow grass there, and it harbors a fungus harmful to horses. It's controlled by mowing the seedheads before they mature (turn white)."

Blackberries are "one of those you gotta stay after," Hendrickson said. He suggested cutting off the plants "as soon as you see green berries" and applying a systemic chemical directly to the exposed roots.

Hendrickson also pointed out differences between bull thistle and Canada thistle. The Canada thistle grows from underground rhizomes, so mechanical control is useless. It requires chemical control in the fall.

"Remember that removing weeds opens up opportunities for other weeds as well as for your grass. Don't stop with weed control," he said. "Good, healthy grass keeps weeds down. Seeds can't compete with good, healthy grass."